Double-layer dual-mode SIW filter using via perturbation

The paper presents a double-layer dual-mode filter with vias on the diagonal inducing the coupling between high order modes TE₁₀₂ and TE₂₀₁. Symmetric transmission response and four transmission zeros (TZs) in the double-layer case are implemented based on substrate integrated waveguide (SIW) technology. An inset feeding is used to achieve the impedance matching, and location shift of the feeding lines has been adopted so as to acquire balanced responses. Two adjacent SIW cavities are coupled through a slot on the common ground plane. As a result, the proposed double-layer dual-mode SIW filter not only largely reduces the dimension, but also occupies a good out of band rejection performance.